measured my tires. Center to center on the front tires is 41 1/2". The back is 40 1/2". So a single long rail on each side could not centered on both front and back tires. Might that be problematic? And those long rails are pricey!
Like
@JayPo said, mount the center of the rail at 41". Or, if you plan on getting bigger tires, go a bit wider apart. The straps themselves are about 2" wide and my front tires are 9" wide, backs are 11", so there's plenty of space for the strap to grab tire tread. They don't have to be perfectly centered, just close enough. That's the other benefit of doing all 4 tires, once it's strapped down it's not moving.
But yeah, went up in price a bit. I got lucky and caught a good sale a while ago, and got 20 feet of e-track, 4 straps, and a bunch of other e-track hookups for well under $100. Unfortunately, it's the "vertical" style, and not "horizontal" style, so It has less places to hook into, but still works.
If you are going this route, look for an e-track kit, with 4x 5' rails. Usually cheaper than trying to get 2 long ones. Quick Amazon search looks like you can still get a 4 pack of 5' rails for about $100 or so.